The National Institutes of Health have required data sharing since 2003. Their Data Sharing Policy page provides the policy, guidance, a data sharing workbook and an FAQ. Starting in January, 2011, the National Science Foundation will require the submission of a two page data management plan as a part of all proposals for NSF grant funding.

This article provides a good overview of the issues involved with establishing an IR

Entire issue on IRs; just a bit dated; Strategies for Institutional Repository Development

ICPSR (Interuniversity Consortium for Political and Social Research)

An international consortium of about 700 academic institutions and research organizations, ICPSR provides leadership and training in data access, curation, and methods of analysis for the social science research community.
ICPSR maintains a data archive of more than 500,000 files of research in the social sciences. It hosts 16 specialized collections of data in education, aging, criminal justice, substance abuse, terrorism, and other fields.